Method of forming fibertapes using rotating mating pressure rolls

ABSTRACT

APPARATUS FOR CONTINUOUS PRODUCTION OF FIBERTAPES, WITH ELIMINATION OF SUBSEQUENT SEPARATE SLITTING OPERATIONS COMPRISING A PAIR OF ROTATABLE PRESSURE ROLLS WITH CONTINUOUS CIRCUMFERENTIAL GROOVES ON THEIR SURFACE, THE ROLLS BEING SO POSITIONED SIDE BY SIDE THAT EACH MALE MEMBER OF THE GROOVED SURFACE OF ONE ROLL FITS INTO THE CORRESPONDING FEMALE MEMBER OF THE OTHER ROLL; AND A METHOD FOR PRODUCTING FIBERTAPES BY INTRODUCING STAPLE FIBERS AND A POLYMERIC BONDING AGENT BETWEEN SUCH ROTATING GROOVED PRESSURE ROLLS.   D R A W I N G

E. BOBKOWICZ ETAL 3,567,545 METHOD OF FORMING FIBERTAPES RISING ROTATING MA'I'ING PRESSURE ROLLS March 2, 1971 Filed May 14, 1968 4 Sheets-Sheet 1 FIG. 5

March 2, 1971 05 0w z EI'AL METHOD OF FORMING FIBERTAPBS RISING ROTATING MATING PRESSURE ROLLS Filed May 14. 1968 4 Sheets-Sheet 2 FIG 6 N ENTOR March 2, 1971 BOBKOWlcz EI'AL 3,567,545

METHOD OF FORMING FIBERTAPES RISING ROTATING MATING PRESSURE ROLLS Filed May 14, 1968 4 Sheets-Sheet I Qfa 244/ as //a 1 x 3. 1 /4 39 Ma, 3 [/6 x 40 3 6b a, \X 3 1 4 *7 f k 42 4a 45 5/ 44 4647 f r 13 March 2, 1971 BOBKOWICZ ETAL 3,567,545

METHOD OF FORMING FIBERTAPES RISING ROTATING MATING PRESSURE ROLLS Flled May 14 1968 4 SheetS--Sheet 4 United States Patent 3,567,545 METHOD OF FORMING FIBERTAPES USING ROTATING MATING PRESSURE ROLLS Emilian Bobkowicz and Andrew J. Bobkowicz, both of 1435 St. Alexander St., Room 310, Montreal, Quebec,

Canada Filed May 14, 1968, Ser. No. 729,090 Claims priority, application Canada, Sept. 26, 1967,

Int. Cl. 1329c /00 US. Cl. 156-229 21 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to the production of fibertapes. (2) Description of the prior art It is known to manufacture fibertapes by contacting staple fibers with a suitable tacky polymer substrate, consolidating the resulting combination by passing it through a pair of smooth pressure roles to form a web and slitting said web into tapes of desired width.

These basic steps of fibertape production have always remained the same, although many improvements have been incoroporated thereto depending on the properties of the desired tape and its ultimate use. Thus, the consolidating step may be accompanied by heating and/or cooling operations. As adhesive material there may be employed polymeric materials having different desirable properties (e.g. insulating, strengthening, etc.); these materials may also be subjected to additional treatments such as molecular orientation and the like.

For example applicants own US. Pat. No. 3,347,727 of Oct. 17, 1967 discloses a method for the production of textured filament yarn, which involves as an intermediate step the formation of composite fibertapes or ribbons. According to this method, a soft layer of resin is extruded through an extrusion head, stretched in the longitudinal direction to cause orientation of the resin molecules, contacted while still tacky with a fibrous web or the like on one or both sides thereof, then the resulting combination is pressed by a pair of rolls with simultaneous cooling to form a composite web which is finally slit longitudinally into a plurality of tapes. The latter are subsequently transformed into yarn by means of a twisting operation.

It is also disclosed in this patent that the extruded layer of resin may be in the form of a film or of a plurality of parallel filaments.

One will readily realize that this particular method equally comprises the above mentioned basic characteristics, namely consolidation by a pair of smooth pressure rolls to obtain a composite web and slitting the latter into tapes.

These two basic features have significant disadvantages. First, the consolidation of the polymeric substrate or resin with staple fibers by a pair of smooth pressure rolls makes it extremely difficult to properly control the shape and 3,567,545 Patented Mar. 2, 1971 surface characteristics of the resulting tape. What actually occurs is that the polymeric substrate or any other adhesive passing together with staple fibers between two smooth pressure rolls is squeezed thereby so that there is a definite flow of the substrate toward the sides of the rolls. The fibers which are in contact with the substrate also tend to fiow sideways therewith and the resulting tapes will have a heavy fibrous texture while others will consist almost entirely of the polymeric substrate. This unevenness of shape, composition and surface texture is of course very undesirable.

If the polymeric substrate or resin is introduced between the rolls in the form of a plurality of filaments, then each filament will be squeezed and will result in a narrow strip; the fibers will mainly attach at the side of each strip, some of them providing interconnection from one strip to another. However, the middle of each strip will remain almost entirely fiberless. The surface of the resulting web will therefore mainly consist of longitudinal fibrous strips and of resinous substantially fiberless strips in between. When this web is slit to form tapes, the latter will more often than not have a very uneven composition and surface structure unacceptable for many applications.

Thus, with the use of conventional smooth pressure rolls, the control of the surface characteristics as well as of other properties, such as the fiber density distribution, the amount of fibers and polymer per tape, etc., is rather difficult and it is almost impossible to obtain, in this way, fibertapes having a polymeric core uniformly covered with staple fibers.

Second, the web slitting operation which is carried out with conventional methods and machinery, including the method disclosed in the above mentioned applicants US. Pat. No. 3,347,727 is in itself a rather difiicult procedure especially for the production of narrow light weight tapes capable of being transformed into yarn or used as such.

For example, if an extrusion technique is used for tape production, the polymeric substrate or resin may easily be extruded at speeds over 200 ft./mi11. Practical extrusion speeds may even reach 1000 ft./min. The fibrous material may also be supplied at any predetermined speed. However, slitting of the resulting web at such speeds can constitute a serious technological obstacle. Since the obtained web has a fibrous or flimsy structure, it does not render itself well to slitting at speeds over 40-50 ft./min. without seriously damaging or even destroying the tapes. Actually one would exclude speeds of 200 ft./min. and over for properly slitting such fibrous webs.

For this reason the slitting operation is economically disadvantageous in the fibertape manufacture. It slows down the whole process and is definitely incompatible with the speeds of modern textile machinery. It must be performed separately from the other tape forming operations and hence an additional cost and disadvantage.

SUMMARY OF THE INVENTION An object of the present invention is therefore to provide a process and an apparatus which will enable easily to control the surface texture characteristics, the structure and other properties of the composite fibertapes and, besides, will eliminate the slitting operation altogether as a separate step by combining the separation of the individual tapes with the tape forming operation, thus overcoming the above mentioned disadvantages.

Another object of the invention is to provide a process and an apparatus which will make it possible to produce under controllable conditions, at high speeds and with great efficiency fibertapes having substantially even surface texture and fiber and polymer distribution of the composite structure.

Still another object of the instant invention is to provide a method and an apparatus which will be compatible 3 with modern extrusion techniques in fibertape manufacture.

Further objects and advantages of the invention will be made evident from the following more detailed description thereof.

Generally, the method according to the present invention comprises introducing staple fibers and a tacky polymer substrate in between a pair of rotating grooved pressure rolls with continuous circumferential grooves (preferably of square cross section) on their surface, said rolls being so positioned face to face that each male member or knife of the grooved surface of one roll fits into the corresponding female member or groove of the other roll thus forming cutting edges for the separation of the staple fibers webs while the tapes are produced. In this manner there is formed within each groove a closed space or cavity in which the polymer is continuously compressed together with staple fibers, if necessary with cooling, to effect consolidation. Each such space or cavity is used to form a separate tape and it can be compared to a molding cavity in which under compression the final molding of the shape takes place. This enables an easy control of the operation within each space or cavity at the time of consolidation, i.e. control of the amount of polymer and fibers to be introduced into each space or cavity, of the depth of each cavity, of the compression to be applied to restrict the fiber distribution and polymer flow within said cavity at the nip of the rolls.

The resulting separate tapes will have a Width defined by the grooves of the rolls, they will possess improved interblending of fiber and polymer and controlled surface and blend characteristics and will need no separate slitting when they are delivered by the grooved pressure rolls already operated.

The novel method is particularly well applicable for the production of narrow tapes, e.g. 4 inch wide or narrower.

It is, of course, unnecessary that the grooves of each roll be of equal width. Actually one roll may be provided with varying in width grooves with corresponding in width members or cutters adapted to enter said grooves. In addition one roll may be provided with very narrow grooves while the other will have corersponding narrow male members or cutters adapted to enter such grooves. Under such conditions the width of each of the resulting tapes will substantially correspond to the width between the cutters.

In a preferential embodiment of the invention, the polymer substrate consists of a layer of resin in the form of directly extruded film or parallel strands of any desired shape (e.g. round filaments, square strands, etc.), which layer while still tacky is contacted on one or both sides thereof with a layer of loosely held staple fibers and then introduced in between the grooved rolls of the type described above, which are driven at a speed higher than the extrusion speed of the resinous layer. This enables to produce fibertapes with the above mentioned advantages and, furthermore, having a resinous core substantially oriented in the longitudinal direction due to stretching of the layer of resin by the rapidly rotating grooved rolls.

The improved apparatus according to the present invention comprises, instead of the usual fiat surface smooth pressure rolls, a pair of grooved rolls such as those described above. Separate slitting means are therefore entirely eliminated.

It is to be noted that the novel apparatus enables the manufacture of ready fibertapes at speeds much in excess of those which were formerly possible because of the elimination of separate slitting means and operations. It provides a solution of dividing the composite fibrous material and polymer substrate into separate tapes of desired width right at the moment of their contact with each other and their consolidation.

The tapes are indeed in their final form as they come out of the grooved rolls and may simply be collected on a suitable wind-up roll.

BRIEF DESCRIPTION OF THE DRAWINGS Several nonlimitative embodiments of the invention will now be described with reference to the appended drawings in which:

FIG. 1 diagrammatically represents the basic principle of a preferred embodiment of applicants novel tape mak ing process and apparatus;

FIG. 2 is a top view of line AA of FIG. 1, showing the engagement of the grooved rolls according to this vention;

FIG. 3 is another top view at line AA of FIG. 1, showing an alternative design of the grooved rolls according to the invention;

FIG. 4 is an enlarged view at line BB of FIG. 1 showing the tapes obtained according to the present invention;

FIG. 5 is a cross-section along line CC of FIG. 4, showing, in section, the tapes obtained;

FIG. 6 is a perspective view of a basic tape making apparatus adapted to be used according to the present invention;

FIG. 7 is a perspective view of a more detailed tape making installation adapted to be used according to the present invention;

FIG. 8 is a diagrammatic view of another apparatus suitable to be used for the fibertape manufacture according to this invention.

It should be noted that same reference numbers are employed to identify same parts in all figures of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 extruder 10, with extruder die 11, is used to extrude a curtain of strands 12 which curtain is then picked up by a pair of grooved rolls 15 and 16 while being contacted, at the nip of said rolls, with layers of loosely held staple fibers 13 and 14. The resulting series of tapes 18 are guided and held under tension by roller 17 and then wound on roll 19. Depending on the desired properties of the fibertapes, the employed staple fibers may be arranged in a substantially parallel manner or at random.

The grooved rolls 15 and 16 can be of a type such as shown in FIG. 2, having square shaped grooves 20 adapted to receive corresponding square shaped protruding members of knives 21. The grooves on roll 15 need not be of the same size as those on roll 16, and this may result in a situation illustrated in FIG. 3 where grooves 20a of roll 15 are very narrow and are adapted to receive narrow protruding members or cutters 21a of roll 16 thereinto. On the other hand the grooves or spacers 22 of roll 16 in FIG. 3, are much wider and actually control the ultimate width of the resulting tapes; the protruding shoulders 23 of roll 15 are also correspondingly wider and are adapted to fit into the grooves 22.

Fibertapes 18 are individually bonded and consolidated in spaces between grooves 20 and knives 21 of FIG. 2 and grooves 22 and shoulders 23 of FIG. 3; in the latter case members 21a are solely used as cutters, while shoulders 23 are used for compressing and consolidating the tapes.

Rolls 15 and 16 may be of steel or any other suitable material.

In FIGS. 4 and 5 the resulting fibertapes 18 with a regular fiber distribution on their surfaces, are shown in an enlarged manner.

FIG. 6 represents a simple combination according to an embodiment of the present invention wherein a suitable polymer is introduced into the extruder 10 through feed hopper 24. The extruder is operated by motor 27 and its position relative to the rolls 15 and 16 is adjusted by means of the height adjusting column 25. The operating conditions of the apparatus are controlled by the instrumentation panel 26.

The curtain of polymer Strands 12 is extruded through the extruder die 11 and is picked up by the grooved pressure rolls 15 and 16 of a design such as illustrated in FIGS. 2 and 3. At the same time there are introduced in between said grooved rolls 15 and 16, on both sides of the curtain 12, layers 13 and 14 of loosely held staple fibers properly directed toward the nip of said grooved rolls by means of deflecting or distributing plates 29 and 30. Rolls 15 and 16 are driven at a speed substantially higher than the extrusion rate of the polymer curtain 12 upon the die to achieve stretching and molecular orientation of the latter, but the polymer is still in tacky condition during its contact with the staple fibers at the nip of said grooved rolls. The resulting tapes 18, separated at the nip point of the grooved rolls, are of the type illustrated in FIGS. 4 and they pass over the guide and tension rolls 17 and 31, and are wound on collecting roll 19 with the help of a proper pressing roller 32. The entire combination may be designed in the form of a handy and compact apparatus placed within a frame 28.

FIG. 7 shows a somewhat more complex device with two extruders a and 10]) comprising respective extruder dies 11a and 11b. According to this particular embodiment, a thermoplastic resin is introduced into hopper 24a and therefrom passes into the extruder 10a. The extruder is driven by motor 27a and its position is adjusted by cylinder 25a. The different operating conditions are indicated and controlled by the instrumentation panel 26a.

The polymer extruded from the extruder die 11a, in the form of a curtain of parallel strands 12a, is cooled and consolidated by roll 33 held at a controlled temperature and then gripped and forwarded by a first set of godet rolls 34, 35 and 36. Said first set of godet rolls, including roll 33, operate at a faster surface speed than the speed of extrusion of the strands 12a issuing from the die 110, thus achieving the first partial degree of orientation in the polymer. To accomplish a fuller degree of orientation, the partially oriented polymer curtain is passed over a heater 37 to heat it up again to a controlled degree, and is gripped again by a second set of godet rolls 38, 39 and 40, said second set of godet rolls operating at a controllable substantially higher surface speed than the said first set of godet rolls (from 3 to 10 times faster for instance) and thus stretching said curtain of strands 12a between said first and second sets of godet rolls, while said curtain 12a is being heated thus obtaining the final and full desired degree of molecular orientation in said strands. The final degree of orientation is controlled by the temperature of the polymeric strands at stretching and the ratio of surface speeds of the second to first sets of godet rolls.

At the same time a polymer, which may be the same or different from the one extruded by extruder 10a, is supplied from hopper 24b into a second extruder 10b. This extruder is driven by motor 271) and its position relative to rolls l5 and 16 is adjusted by height adjusting cylinder 25]). The operating conditions of this extruder are controlled by means of the instrument box 26b.

A second curtain of strands 12b is thus extruded from extruder die 11b and into the nip of a pair of grooved pressure rolls 15 and 16. This second curtain 12b is combined with the first curtain 120 which has been oriented to the fullest possible extent before both curtains are picked up by the grooved pressure rolls 15 and 16. The strands of the first curtain 12a are preferably made to fall in between those of the second curtain 12h. In order to impart some tackiness to the curtain 12a, the latter may be warmed up by passing it over a heated deflecting plate 41. Also it is sufficient to deflect this first curtain close to the hot extruder die 11b to soften it and to impart some tackiness thereto.

The so combined first and second curtains 12a and 12b are then contacted on both sides thereof, at the nip of the grooved pressure rolls 15 and 16, with layers of loosely held staple fibers 13a and 14a which come out of fiber desintegrating devices 44 and and are forwarded toward the nip of the grooved pressure rolls by means of supporting members and 51. The obtained combination is pressed and consolidated as already described above and the resulting tapes 18 pass alternatively over stripping rolls 52 and 53 for easier separation, then they are brought together at the nip of a pair of smooth pull rolls 54 and 55, if necessary with some additional longitudinal stretching, and finally wound on a large collecting roll 19 after passing through a slot of a guiding member 56.

The obtained fibertapes have excellent longitudinal strength in view of the fact that they contain some strands 1211 which have been oriented to the fullest extent, while strands 1211 have been used mainly for imparting tackiness to enable interbonding and consolidation of the staple fibers with the strands.

The fibers which are contacted with the polymer strands to form the fibertapes have been produced from fiberwebs 42 and 43 which may consist of a same or different material. The manner in which the web is disintegrated into fibers is described here-below for web 42 only in the form of a nonlimitative example.

Thus, web 42 is pulled by rolls and 61 into disintegrating device 44 where it is broken down into fibers by means of licker-in rolls 46. The resulting fibers are then sucked through passage 47 onto the surface of a perforated drum 48 by a stationary suction device 49 posi tioned within said drum. The layer of loosely held fibers 13a resulting on said drum 48 is then transmitted via support member 50 by the rotation of the drum 48 toward the nip of said grooved pressure rolls 15 and 16. A more detailed description of this staple fiber producing, positioning and forwarding arrangement has been made in applicants Canadian Pat. No. 747,101 of. Nov. 29, 1966.

An alternative or additional fiber web supply embodiment is also described below in the form of a nonlimitative example. The layers of loosely held fibers 13a and 14a described above are at random arranged because of the inherent properties of the licker-in device 44 which is used. Substantially parallel arranged webs of staple fibers may be desired in addition to or in lieu of at random arranged layers 13a. 14a, and such webs 13b. 14b with parallel arrangement of fibers may be supplied by means of a standard textile drawframe arrangement embodied within the apparatus but not illustrated here in detail.

The entire combination may be embodied within frame 28 to form an efficient fibertape producing apparatus constituting one embodiment of the present invention. Additional Winder 57 may also be provided for automatically changing collecting rolls 19, and thus operating the apparatus continuously, since the resin and fiber supplies are fed in on a continuous basis.

FIG. 8 shows a still further embodiment of the present invention. According to this embodiment a layer 12 of a thermoplastic polymeric material is extruded through the extrusion die 11 of extruder 10. The layer 12, which may be in the form of a film or plurality of parallel filaments or strands of any configuration, is then stretched between the die 11 and the first set of godet rolls 34, 35, and 36, including the consolidation roll 33, and further stretched between said first set of godet rolls and a second set of godet rolls 38, 39 and 40, while being warmed up over heater 37, so as to achieve orientation and strength of the polymeric material in a similar manner as described above for FIG. 7. Thereupon, the oriented polymeric layer 12 is guided over roller 58 and into and through a heater 59 with controlled temperature conditions. The temperature in this heater is such as to enable the polymeric material to acquire surface tackiness substantially without losing its inner molecular orientation.

The so treated polymeric layer is then introduced, as in previous cases, in between two grooved pressure rolls 15 and 16 together with layers of staple fibers 13 and 14 at each side thereof. The resulting fibertapes 18 are then alternatively passed over stripping rolls 52 and 53 for easier separation and after being properly guided by the guiding member 56 they are wound on the collecting roll 19. Device 57 is intended to provide an alternative collecting roll when the first one is full.

Although layers 13 and 14 of staple fibers can be formed by any suitable means, in this particular embodiment they are obtained by disintegration of fiberwebs into individual fibers and electrostatic parallclization of the resulting fibers as already described and claimed in applicants copending US. patent application No. 461,912 ofJune7, 1965.

This is done by braking up the webs 42 and 43 of staple fibers, which can be of same or different nature, by means of licker-in rolls 46 and 46a after said webs have been introduced into the disintegrating chambers by supply rolls 60, 61 and 60a, 61a respectively. The distintegrated fibers 47, 470 are carried by a source of compressed air 62, 62a in between two pairs of converging electrodes 63, 64 and 63a, 64:: respectively where they are parallelized by the converging electrostatic field. The resulting parallel arranged fibers are then deposited by suction on perforated rotating drums 48. 48a provided with suction devices 49, 49a therewithin and are forwarded toward the nip of grooved pressure rolls 15, 16 with the help of supporting members 50, 51.

The basic apparatus for fibertape manufacture according to one preferred embodiment of this invention will comprise:

(a) A pair of rotatable grooved pressure rolls 15 and 16 provided with continuous circular grooves on their surface and positioned face to face so that each male member of the grooved surface of one roll fits into the corresponding female member of the other roll, and the sharp edges of which simultaneously act as cutters for separation of each tape;

(b) Means (extruder and extruder die 11) for extruding a layer of resin 12, in the form of a film or of a curtain of parallel strands, toward the nip of said grooved pressure rolls and 162 (c) Means for simultaneously supplying a layer of loosely held staple fibers 13 and/or 14 toward the mp of said grooved pressure rolls on at least one side of the extruded layer of resin;

((1) Means for rotating the grooved pressure rolls preferably at a higher speed than the rate of extrusion of the layer of resin so as to pick up said layer of resin and stretch it in longitudinal direction to cause molecular orientation of said resin; and

(e) Means for separating and collecting the fibertapes obtained through consolidation of the layer of resin with the staple fibers within the grooves of the pressure rolls.

One will easily realize that this apparatus does not necessitate any separate slitting means.

If desired, the grooved pressure rolls may be provided with a cooling arrangement to assist the coagulation of the extruded resin during its consolidation with the staple fibers.

In addition there may also be provided means for proper distribution of the staple fibers at the nip 0f the grooved pressure rolls, enabling control of the fibrous surface texture of the resulting tapes.

A more complex fibertape producing apparatus according to another embodiment of the invention will comprise:

(a) A first extruder 10a adapted to cxtrude a first curtain of thermoplastic strands 12a;

(b) Means for stretching said strands in longitudinal direction to cause their fullest possible molecular orientation;

(c) A second extruder 10b adapted to extrude a second curtain 12b of polymeric strands;

(d) Means for combining said first curtain 12a with said second curtain 12b so that the strands of the latter will be in staggered relation with respect to those of the former and form a single combined curtain of parallel filaments;

,(e) A pair of rotatable grooved pressure rolls 15 and 16 provided with continuous circular grooves on their surface and positioned face to face so that each male member of the grooved surface of one roll fits into the corresponding female member of the other roll and the sharp edges of which act as tape separation means;

(f) Means for supplying the combined curtain of parallel strands toward the nip of said pressure rolls 15 and 16 while at least some of them in each groove are in tacky condition;

Means for disintegrating two solid fiberwebs, one on each side of the combined curtain of parallel strands, into individual loosely held staple fibers;

(h) Means for forwarding the loosely held staple fibers toward the nip of said grooved pressure rolls 15 and 16 with proper distribution;

(i) Means for rotating the grooved pressure rolls so as to pick up the combined curtain of strands together with the loosely held staple fibers to separate and consolidate the same; and

(j) Means for collecting the resulting fibertapes 18 coming out of the grooved pressure rolls.

In this particular embodiment, the means for stretching the strands extruded from the first extruder may consist of two sets of well known godet rolls with a suitable heater in between. Thus, the curtain of thermoplastic resin is stretched once to effect partial orientation, then it is heated and stretched once again to complete said orientation.

The means for disintegrating two solid fiberwebs into loosely held fibers and forwarding the latter, with proper distribution, toward the nip of the grooved pressure rolls, may consist of licker-in rolls and perforated drums such as those illustrated in FIG. 7 and described above and/ or of a conventional standard drawframe.

Finally, according to still another embodiment of the invention there may be provided a fibertape making apparatus comprising:

(a) An extruder adapted to extrude a layer of thermoplastic resin in the form of a film or of a curtain of parallel strands;

(b) Means for stretching said layer of resin in longitudinal direction to cause its fullest possible orientation;

(c) A heater, preferably of tunnel type, with means for precise control of temperature therein;

(d) Means for passing the oriented layer of resin through said heater, so as to soften the surface thereof while maintaining its inner molecular orientation;

(e) A pair of rotatable grooved pressure rolls provided with continuous circular grooves on their surface and positioned face to face so that each male member of the grooved surface of one roll fits into the corresponding female member of the other roll and the sharp edges of which act as tape separation means;

(f) Means for forwarding the softened layer of resin toward the nip of said grooved pressure rolls;

(g) Means for disintegrating two solid fiberwebs, one on each side of the softened layer of resin, into individual loosely held staple fibers;

(h) Means for supplying the loosely held staple fibers toward the nip of said grooved pressure rolls with proper distribution;

(i) Means for rotating the grooved pressure rolls so as to pick up the softened layer of resin together with the loosely held staple fibers to separate and consolidate the same; and

(j) Means for collecting the resulting separate fiberta 8.

l: has been experimentally found that it is possible, by passing an oriented layer of thermoplastic material in a heater with accurate temperature control and by suitably controlling the temperature, to soften and render tacky the surface of said layer without substantially affecting the layers inner crystallinity and orientation. The temperature necessary to achieve this condition varies for each particular material, as well as the mass of the layer being processed per unit time where the amount of heat applied to the material naturally produces a transient temperature gradient in its cross-section. The necessary heat input level can be easily experimentally determined in each case, and controlled to achieve the surface temperature at which tackiness occurs for a given material while maintaining the core at a lower temperature. This finding is the basis for the above described embodiment of the present invention, which is illustrated in FIG. 8.

In all these embodiments the grooves of the pressure rolls are of substantially square cross section. Also the extruders preferably operate at pressure of about 500- 10,000 p.s.i., a typical operating extrusion pressure is about 2,000 p.s.i.

The tapes obtained according to the instant invention may have many uses. For example, they may be transformed into yarn or they may be employed as such in some textile application, e.g. weaving, knitting, brading etc.

The polymer substrate, which is one of the constituents of the obtained fibertapes, may consist of any extrudable polymer resins or their blends. The thermoplastic resins which are especially suitable are of polyamide, polyester and polyolefin type (e.g. nylon, polyethylene, acrylonitrile, etc.).

The staple fibers may consist of wool, cotton, bast fibers, man-made fibers and mixtures thereof.

It should, of course, be understood that the invention is not limited to the specifically described embodiments but that many modifications evident to those skilled in the art can be made without departing from the spirit of the invention and the scope of the following claims.

We claim:

1. Method for the production of fibertapes comprising introducing staple fibers and a tacky polymer substrate between a pair of rotating pressure rolls having continuous circumferential grooves and positioned face to face so that each male member of the grooved surface of one roll fits into the corresponding female member of the other roll to form at the nip point of said rolls cavities adjustable in depth and having shearing edges adapted to separate the resulting composite staple fiberpolymer substrate material into a plurality of fibertapes, with simultaneous consolidation of said fibertapes within said cavities.

2. Method according to claim 1, in which the grooves of said rolls are of substantially square cross-section with sharp edges to achieve positive cutting action at the nip point of the rolls.

3. Method according to claim 1, further comprising externally controlling the termperature of said grooved pressure rolls.

4. Method for the production of fibertapes in a continuous sequence of operations comprising: extruding a layer of an extrudable polymer substrate through an extrusion die; contacting said polymer layer, on at least one side thereof, with a layer of loosely held staple fibers while the polymer substrate is still in tacky condition; introducing said layers between a pair of rotating pressure rolls having continuous circumferential grooves and positioned face to face so that each male member of the grooved surface of one roll fits into the corresponding female member of the other roll to form at the nip point of said rolls cavities adjustable in depth and having shearing edges adapted to separate the resulting composite staple fiber-polymer substrate material into a plurality of fibertapes with simultaneous consolidation of said fibertapes within said cavities and collecting the resulting fibertapes in a wind-up operation.

5. Method according to claim 4, in which said rolls are rotated at a speed greater than the extrusion rate of the layer of resin, whereby stretching of the layer of resin with attendant molecular orientation in longitudinal direction is achieved.

6. Method according to claim 4, in which the grooves of said rolls are of substantially square cross-section with sharp cutting edges for fibertape separation.

7. Method according to claim 4, further comprising externally controlling the temperature of the grooved rolls.

8. Method according to claim 4, in which the extruded layer of polymer is in the form of a film or of a curtain of parallel strands.

9. Method according to claim 4, in which the extruded layer of polymer consists of thermoplastic material, thermosetting material or their blends. 10. Method for the production of fibertapes in a continuous sequence of operations comprising: extruding a first curtain of extrudable polymer strands through an extrusion die; stretching said curtain in longitudinal direction to cause molecular orientation thereof; extruding a second curtain of tacky polymer strands through another extrusion die; combining said first curtain of strands with the second curtain of tacky strands to produce a combined curtain of strands having a staggered arrangement; feeding and superimposing a layer of loosely held staple fibers onto at least one side of said combined curtain of strands; introducing said combined curtain of strands and said layer of staple fibers between a pair of rotating pressure rolls having continuous circumferential grooves and positioned face to face so that each male member of the grooved surface of one roll fits into the corresponding female member of the other roll to form at the nip point of said rolls cavities which are adjustable in depth and which have shearing edges adapted to separate the resulting composite staple fiber-polymer substrate material into a plurality of fibertapes with simultaneous consolidation of said fibertapes within said cavities, said combined curtain of strands being so introduced between the rolls that at least one of said oriented and one still tacky polymer strand go into each cavity to achieve in each tape adequate interbonding of said composite fiber-polymer material; and collecting the resulting fibertapes.

11. Method according to claim 10, in which orientation of the first curtain of polymer strands is effected by stretching said curtain in longitudinal direction to effect its partial orientation, re-heating the partially oriented strands, and completing the orientation by effecting another stretching of the reheated strands.

12. Method for the production of fibertapes in a continuous sequence of operations comprising: extruding a layer of an extrudable resin through an extrusion die; stretching said layer of resin in a heater with accurately controlled temperature conditions so as to soften and render tacky the surface of said layer of resin without substantially affecting its inner molecular orientation; forming a layer of loosely held staple fibers on at least one side of said layer of resin; passing the layer of resin with tacky surface and the layer of staple fibers through a pair of rotating grooved pressure rolls having continuous circumferential grooves and positioned face to face so that each male member of the grooved surface of one roll fits into the corresponding female member of the other roll to form at the nip point of said rolls cavities which are adjustable in depth and which have shearing edges adapted to separate the resulting composite staple fiber-polymer substrate material into a plurality of fiber- 1 1 tapes with simultaneous consolidation of said fibertapes within said cavities, and collecting the resulting fibertapes in a wind-up operation.

13. Method according to claim 12, in which the circumferential grooves of said rolls are of substantially square cross-section with sharp shearing edges for fibertape separation.

14. Method according to claim 12, further comprising externally controlling the temperature of said grooved pressure rolls.

15. Method according to claim 10, in which the extrusion is carried under pressure of between 500 and 10,000 p.s.i.g.

16. Method according to claim 12. in which the extrusion is carried under pressure of about 2,000 p.s.i.g.

17. Method according to claim 10, in which the first curtain of strands is softened and rendered tacky prior to its being combined with the second curtain.

18. Method according to claim 10, in which the curtains of strands consist of resins of polyamide, polyester or polyolefin type or their combinations.

19. Method according to claim 10, in which the loosely held staple fibers have a substantially parallel or random arrangement.

20. Method according to claim 12, in which the layer of resin is in the form of a film or of a curtain of parallel strands.

2l. Method according to claim 12, in which orientation of the layer of resin is elfected by stretching said layer in longitudinal direction to effect its partial orientation, reheating the partially oriented layer, and completing the orientation by efiecting another stretching of the reheated layer.

References Cited UNITED STATES PATENTS 3,083,133 3/1963 Hansen et al. l56298X 3,343,370 9/1967 Twele et al. 156-298X 3,347,727 10/1967 Bobkowicz et al l56244 BENJAMIN R. PADGETT, Primary Examiner S. J. LECHERT, ]R., Assistant Examiner US. Cl. X.R. 

